Steam generation apparatus and associated control system and methods for startup

ABSTRACT

The current disclosure relates to a method of steam generation. Particularly, the current disclosure relates to steam generation supply apparati and associated control systems that are used for enhanced oil recovery. Certain embodiments are provided including methods and associated control systems related to the startup as well as main steam pressure header control or maintenance of a desired steam quality for such steam generation systems during normal operation.

REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.14/030,618, filed Sep. 18, 2013, which is hereby specificallyincorporated by reference herein in its entirety.

TECHNICAL FIELD

The current disclosure relates to steam generation apparati andassociated control systems. Particularly, the current disclosure relatesto such steam generation apparati and associated control systems thatare used for enhanced oil recovery.

BACKGROUND

Steam generation apparati are used in a host of industries includingfood preparation, cleaning, heating and power generation sectors.Another industrial sector that uses steam generation apparati includesenhanced oil recovery projects where steam is injected into thereservoir through injection wells located in rock that has fluidcommunication with production wells. The purpose of steam injection isto increase reservoir pressure and temperature to displace hydrocarbonstoward a pumping well. This allows more oil to be recovered than wasinitially possible during the primary drilling and oil extraction phaseof an oil well. As can be imagined, such steam generation apparatirequire that a number of process variables and associated equipment becontrolled during startup and continuous normal operation. Accordingly,a need exists for an apparatus that manages such variables efficientlyduring startup and continuous normal operation.

SUMMARY

Disclosed is an apparatus for supplying a flow of at least one of waterand steam to a desired destination or to a venting reservoir comprisinga feedwater supply system, a steam generation system and a deliverysystem that includes a main steam header pipe that runs from the steamgeneration system to the desired location and a vent pipe that branchesfrom the main steam header pipe to the venting reservoir. It furtherincludes a plurality of instruments and devices that are in operativeassociation with the feedwater supply system or delivery systemconfigured for sensing physical parameters of at least one of water andsteam for controlling the flow and a control system that includes aninput device, output device and memory, the control system being inoperative association or communication with the instruments and devices.

Also disclosed is a method of starting up an apparatus capable ofproducing at least one of water and steam of varying quality, theapparatus including a feedwater supply system that includes a feedwaterpump, a steam generation system and a delivery system that includes amain steam header pipe that runs from the steam generation system to adestination, and a vent pipe that branches from the main steam headerpipe and that runs to a venting reservoir. The method includes thefollowing steps: determining whether it is permissible for the feedwaterpump to run; and sending at least one of water and steam to the ventingreservoir.

Various implementations described in the present disclosure may includeadditional systems, methods, features, and advantages, which may notnecessarily be expressly disclosed herein but will be apparent to one ofordinary skill in the art upon examination of the following detaileddescription and accompanying drawings. It is intended that all suchsystems, methods, features, and advantages be included within thepresent disclosure and protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and components of the following figures are illustrated toemphasize the general principles of the present disclosure.Corresponding features and components throughout the figures may bedesignated by matching reference characters for the sake of consistencyand clarity.

FIGS. 1A and 1B are different perspective views of a trailer mountedunit of an embodiment of a steam generating apparatus of thisdisclosure.

FIG. 1C is a simplified schematic of a feedwater supply system and asteam generation system of an embodiment of a steam generating andsupplying apparatus of this disclosure.

FIGS. 2A1, 2A2, 2B1 and 2B2 provide legends so that the other detailedschematics of embodiments of this disclosure can be more readilyunderstood. Specifically, they convey the meaning and function ofcertain components represented symbolically in the schematics includingvalves, flow elements, flow meters, level instruments, pumps, motors,blowers, fans, turbines, dampers, pressure instruments,strainers/filters, temperature instruments, controls, and miscellaneousitems.

FIG. 2C is a detailed schematic of a feedwater supply system of anembodiment of a steam generating and supplying apparatus of the presentdisclosure.

FIG. 2D is a detailed schematic of a steam generating system of anembodiment of an apparatus of the present disclosure that receivesfeedwater from the supply system of FIG. 2C.

FIGS. 2E1, 2E2 and 2E3 are segments of a detailed schematic of a steamand/or water delivery system of an embodiment of an apparatus of thepresent disclosure that receives steam and/or water from the steamgenerating system of FIG. 2D.

FIGS. 3A, 3B and 3C are segments of a detailed schematic of a burner ofthe steam generating system shown in FIG. 2D along with the associatedinputs, outputs and control system.

FIG. 4 is a flowchart outlining the various steps of a method forstarting up a steam generating apparatus according to one embodiment ofthe present disclosure.

FIG. 5A is a flowchart outlining the various steps of a method orroutine for attaining a desired injection pressure that is supplied bysteam generating apparatus according to one embodiment of the presentdisclosure.

FIG. 5B is a flowchart showing the various steps of a sub-process orsubroutine for the step of determining whether the injection pressure ata desired location is within acceptable parameters as shown in FIG. 5A.

FIG. 5C is a flowchart of a method or routine similar to that disclosedin FIG. 5A wherein a control system is used and various controls for thefeedwater flow rate and the injection pressure are placed into automaticmode and the desired parameters for the flow rate and the injectionpressure are inputted into the control system.

FIG. 6 contains a flowchart for maintaining the main steam header pipepressure within acceptable parameters using a valve that is configuredto send steam and/or water to a venting reservoir when needed.

FIG. 7A shows a flowchart for a method or routine in generalized stepsfor predicting and attaining a desired steam quality made by a steamgenerating apparatus according to one embodiment of the presentdisclosure.

FIG. 7B shows a flowchart showing a sub-process or subroutine for thestep of estimating the enthalpy of the desired steam quality of thesteam and/or water mixture based on the current vapor and liquidenthalpies of the steam and/or water mixture shown in the flowchart ofFIG. 7A.

FIG. 7C depicts a flowchart showing a sub-process or subroutine forcalculating boiler inefficiency that may be used to adjust the amount ofheat calculated to be needed to be input to the feedwater as determinedin a step of the process shown in FIG. 7A.

FIG. 7D shows a flowchart that illustrates the sub-process or subroutineand its associated steps for calculating the adjusted gross heat inputrate depending on the type of fuel that is being used.

DETAILED DESCRIPTION

Disclosed is a steam generation apparatus, control system and associatedmethods, systems, devices, and various architectures. The steamgeneration apparatus includes a feedwater supply system, a steamgenerating system, a steam and water delivery system and a controlsystem that is operatively associated and/or in communication with anyor all of these systems. Also, various methods or protocols aredisclosed for operating these various systems in several phasesincluding startup and normal operation. It would be understood by one ofskill in the art that the disclosed steam generation apparatus, controlsystem and associated methods are described in but a few exemplaryembodiments among many. No particular terminology or description shouldbe considered limiting on the disclosure or the scope of any claimsissuing therefrom.

Steam injection is a common method of extracting heavy oil. It isconsidered an enhanced oil recovery (EOR) method and is the main type ofthermal stimulation of oil reservoirs. There are different forms of thetechnology, with the two main ones being Cyclic Steam Stimulation andSteam Flooding. Both are applied to oil reservoirs relatively shallowand that contain crude oils, which are very viscous at the temperatureof the native underground formation. Steam injection is widely used inthe San Joaquin Valley of California (USA), the Lake Maracaibo area ofVenezuela and the oil sands of northern Alberta (Canada) to name but afew locations. Steam flood, known as a steam drive, wells are used assteam injection wells and other wells are used for oil production.

Two mechanisms are at work to improve the amount of oil recovered. Thefirst is to heat the oil to higher temperatures and to thereby decreaseits viscosity so that it more easily flows through the formation towardthe producing wells. A second mechanism is the physical displacement inwhich oil is pushed to the production wells. While more steam is neededfor this method than for the cyclic method, it is typically moreeffective at recovering a larger portion of the oil. Cyclic and steamflooding techniques are but a few of the methods to which the disclosedembodiments may be applied, but it is contemplated that other methodscurrently used in the art or that will be devised in the art could beused with the disclosed embodiments.

The intent is to reduce the viscosity of the bitumen to the point wheregravity will pull it toward the producing well. Locations where suchsteam injection is employed vary in certain embodiments. Hence, thesteam generating apparati disclosed herein may be mounted on portableplatforms such as barges or truck trailers so that they can betransported to a site where oil and steam injection wells are located.In other embodiments, the steam generating apparatus is locatedpermanently at the site. Of course, the embodiments disclosed herein arenot limited merely to oil recovery applications, which include both theSteam Flooding and Cyclic techniques as well as others, but it iscontemplated that the embodiments discussed herein may be applied toother industrial sectors as well. Also, the quality of the steam, whichis the mass fraction in a saturated mixture that is vapor, produced bythe embodiments disclosed herein may be varied from 0 to 100 percent. Inmany applications, the desired steam quality ranges from 50 to 100percent and may be as high as 80 to 90 percent.

One embodiment of a steam generation and supply apparatus 100, which isat least partially portably mounted on a trailer platform, is disclosedand described in FIGS. 1A and 1B. The steam generation and supplyapparatus 100 includes three major systems including the feedwatersupply system 110, the steam generating system 120, and the steam andwater delivery system 130.

The feedwater supply system 110 includes a water tank (not shown), afiltration device (not shown), a preheater (not shown), a booster pump118 (shown in FIG. 1C) and a main feedwater pump 111. In general terms,water is supplied on site from a fresh water source such as a lake ormunicipal water system where it is stored in a water tank and then drawnout or pumped out by the booster pump 118 before being filtered for theremoval of sediment and other impurities via the filtration device thatcould adversely affect the equipment of the apparatus. It is preferableif the water is free from impurities, that is to say, is on the level ofwater filtered by a reverse osmosis device and softened. The water isthen heated slightly by the preheater and the flow rate and pressure ofthe feedwater is then increased by the main feedwater pump 111 so thatit can properly supply the steam generating system 120. In certainembodiments, the feedwater pump is a positive displacement multi-plungerstyle of pump.

The steam generating system 120 includes a pipe in pipe (PIP) heatexchanger 122, a convection section that comprises an extended surfaceeconomizer type heat exchanger 121 and a bare tube type heat exchangersection 124, a radiant heat exchanger section 126 and a burner 128.Again, in general terms, the feedwater enters the PIP heat exchanger 122where its temperature is increased by water already heated as theirseparate flow paths pass each other in a counter-flow arrangement, whichis advantageous, as it is an efficient way to heat the incomingfeedwater as well as help prevent combustion gases from condensing onthe cold tubes found in the extended surface economizer section, whichcould create acid in the boiler that could damage the equipment. Thewater then enters the extended surface economizer 121 which includesfins or other types of extended surfaces for improving heat transferthat help to increase the water temperature further by supplying moresurface area to facilitate heat transfer to the water. The water thenexits out of the extended surface economizer 121 back into PIP exchanger122 past the incoming water in a manner already described, which coolsthe water back down again a slight amount which is advantageous as it isnot desirable to overheat the water and have 100% steam quality in theboiler. The water then enters the bare tube section 124 and then theradiant section 126 of the steam generator whose heat is created by theburning of fuel provided by the burner 128. The bare tube section lacksfins as the combustion gases in the boiler unit in this area would betoo high and would melt the fins. At this point, the majority of thewater has been converted to steam. As will be discussed in more detaillater herein, the fuel rate supplied to the burner is monitored andcontrolled to adjust the amount of heat generated.

However, it is contemplated that other methods or devices known in theart or that will be devised in the art could be used to heat the waterto steam including electric heating, solar heating, etc. Accordingly,the phrase “steam generation system” or apparatus should be construedbroadly herein to include any method or device that is used to heatwater.

Turning now to FIG. 1C, the components of the feedwater supply system110 and the steam generating system 120 and the manner in which theywork together is shown in a simplified schematic format. Water is drawnby the booster pump 118 from a preheated water supply (not shown) to thefeedwater pump 111. The feedwater pump 111 then raises the pressure andflow rate of the water before it reaches the steam generating system. Afeedwater flow rate control loop 113 is provided with a valve 115 sothat the pressure and flow rate of the feedwater can be controlled byopening or closing the valve 115 which effectively changes the amount ofwater sent toward the steam generating system 120. The functioning ofthis control loop will be discussed in more detail later.

The feedwater then enters the PIP heat exchanger 122 into an outer pipe123a that surrounds an inner pipe 123 b, allowing the colder water thatis entering the PIP heat exchanger 122 to run past warmer water found inthe inner pipe 123 b in an opposite direction. As previously described,this inner water has already been heated to a higher temperature by theextended surface economizer 121 of the steam generating system 120.Leaving the outer pipe, the water then enters the extended surfaceeconomizer 121 that includes a region having fins 125 and returns to thePIP heat exchanger 122 through the inner pipe 123b. The water thenpasses through the bare tube section 124. The water then exits the baretube section and passes back through the PIP heat exchanger 122 and thenenters the pipe found in the radiant section 126, where the water isheated through radiation by a flame created by the burner 128 that hasfuel supplied to it as well as air via the combustion air damper 127 andsupply fan 129. The damper actuator controls the position of the airdamper 127 which comprises a series of louvers that move to an openposition. This in turn, regulates the amount of air entering the burner128. Alternatively, the air flow is regulated by controlling the speedof the supply fan with a variable frequency drive that is run by thecontrol system.

Focusing back now on FIGS. 1A and 1B, the water and steam deliverysystem 130 includes a steam quality measuring subsystem 132, a ventingsubsystem 134, a bleed-off or diverter subsystem 136, and a steaminjection subsystem 138. In overview, the steam quality measuring system132 allows for a sample of the steam and water mixture that exits thesteam generating system 120 to be cooled down and analyzed by methods ordevices commonly known in the art to see what portion of the mixture isin fact steam. The venting subsystem 134 provides an avenue for ventingsteam and/or water to atmosphere and/or a reservoir when certainparameters are not within acceptable limits both during startup andduring normal operation. The bleed-off system 136 allows a portion ofthe steam and water mixture to be separated from the mainline of thedelivery system so that it can be fed to auxiliary equipment and/orrecirculated to the feedwater preheater. Finally, the steam injectionsubsystem 138 provides the steam/water mixture to an injection well at adesired pressure and quality. More details of how the delivery system130 works will be given later.

Furthermore, a control system 140 is provided that can help ensure thatthe quality of the steam/water mixture as well as its temperature andpressure is within desired parameters as it is injected into aninjection well. In particular, the control system helps execute severalalgorithms or implements various routines, processes, and methodsdescribed herein that control operation of the apparatus 100 and thatimprove the efficiency as well as the safety and durability of theapparatus 100. For this embodiment, the control system includes a seriesof control units that are in communication with each other through theprogrammable logic controller (PLC) and certain components of theapparatus. The PLC (Allen Bradley Series No.L1756) is programmed asdesired. However, it is contemplated that the control system could beprovided by any other devices or methods known in the art or that willbe devised in the art as is elaborated upon later herein. In otherembodiments, the control system may include a series of control units,instruments, control devices and other components that arecommunicatively connected to a programmable logic controller (PLC). thePLC may represent any PLC known in the art, a general-purpose processorwith a firmware or other memory containing processing logic, afield-programmable gate array (“FPGA”), a distributed control system(“DC S”), or the like.

The control system may further implement input devices, such as atouchscreens, keyboards, trackballs, mice, switches, knobs, and thelike, and output devices, such as displays, dials, gauges, audible andvisible alarm annunciators, and the like, that are in communication withthe PLC. As described herein, a “memory” includes any non-transitorycomputer-readable medium accessible to the PLC or other processor of thecontrol system and used to store data structures, program modules, andother processor-executable code or logic, and does not includetransitory signals. As such, memory may include, but is not limited to,RAM, ROM, EPROM, EEPROM, flash memory or other solid-state memorytechnology, optical disk storage technology, hard disk devices (“HDD”)or other magnetic disk storage, other magnetic storage devices, and thelike. In further embodiments, the control system could be provided byany other devices or methods known in the art or that will be devised inthe art that may implement the routines, processes and methods describedherein for controlling the operation of the apparatus 100 as well asimproving the efficiency, safety, and durability of the apparatus,including a general purpose computer communicatively coupled to thecontrol units, instruments, control devices, and other components of theapparatus and programmed to perform the routines, processes and methodsdescribed herein.

FIGS. 2A1, 2A2, 2B1 and 2B2 provide legends so that the other detailedschematics of embodiments of this disclosure can be more readilyunderstood. Specifically, they convey the meaning and function ofcertain components represented symbolically in the schematics includingvalves, flow elements, flow meters, level instruments, pumps, motors,blowers, fans, turbines, dampers, pressure instruments,strainers/filters, temperature instruments, controls, and miscellaneousitems. As used herein, the term “instruments” may refer to any componentthat is used to measure a physical parameter of water or steam such asflow rate, pressure and temperature. Similarly, the term “device” mayrefer to any component that manipulates the flow of water or steam.However, it is contemplated that either term may be interchanged witheach other. Ultimately, the context of how the term is used should relaythe intended meaning to the reader of this disclosure and the claims.

Turning now to FIG. 2C, a detailed schematic depicting the design of anembodiment of the feedwater supply system 110 following the direction offlow from the main feedwater pump 111 to the steam generating system 120is given. As can be seen, the feedwater pump 111 includes a motorfaceplate 202 that is in integral with the PLC and is displayed on theGUI or HMI of the control system and helps control the operation of thepump. The motor faceplate 202 includes several inputs including a handswitch 204 signal that can be placed in an off or auto position, afeedwater pump vibration high alarm signal 206 that alarms and ishardwired in series with the pump starter contactor that can shut themotor off if the pump vibrates too much, and a feedwater drip oil tanklevel is not low signal 208 that allows the pump to start if sufficientdrip oil is present. Also, a switch 209 is hardwired in series with thepump starter contactor and sends a low level alarm to the PLC thatindicates whether the feedwater pump crankcase oil level is not low.Additionally, a feedwater pump run confirmation signal 210 is sent fromthe pump to the motor faceplate 202 once a turn pump on signal 211 hasbeen sent to the pump 111 and the pump begins to run. Of course, thepump can be turned off by a similar signal.

There are two inlets 212 a,b shown on the schematic for the pump 111 andtwo outlets 214 a,b but it is to be understood that this arrangementwould work in a similar fashion as the single inlet and outlet shown inFIG. 1B. There are dampening devices on the pump inlet 216 and pumpoutlet 205 that connect to the pump via inlet 212 b and outlet 214 athat are commonly used in the art for dissipating vibration orpulsations made by the feed pump 111. The first outlet 214 a providesfeedwater to the steam generating system 120 while the second outlet 214b sends water to the flow rate control loop 113 as previously describedwith respect to FIG. 1C. This flow rate control loop includes arecirculation feedwater flow rate control valve 218 (analogous to valve115 of FIG. 1C), and a valve position measuring device 222 associatedwith the control valve 218 and associated control device 224. Also,feedwater flow control valve demand signal device 225 that is incommunication with the PLC is provided.

Immediately before the inlet 212 there is positioned an inlet feedwaterpump pressure indicating instrument 226 and an associated controlsignal/alarm device 228 that can indicate if the feedwater inlet pumppressure is too low as this could damage the pump. Located downstreamfrom the first outlet 214a is feedwater pump outlet pressure indicatinginstrument 230 as well as an associated control device 232. Locatedfurther downstream is a feedwater flow indicating device 234 and anassociated control device 236 that is in communication with the PLC viaa software link to send an alarm 237 if the feedwater flow rate is toolow as this could cause components of the steam generating system 120 tooverheat or be otherwise damaged. The alarm goes to the burnermanagement system (BMS) as a burner run permissive condition, if theflow rate is too low then the burner is shut down. The control signaldevices 232 and 236 are in communication with the feedwaterrecirculation control valve 218 as well as other controls associatedwith the delivery system 130 as will be described in more detail laterfor allowing control of the feedwater flow rate. The methods associatedwith the control of the feedwater flow rate will be elaborated uponlater herein.

FIG. 2D shows a detailed schematic of the steam generating system 120.It receives water from the feedwater supply system just described andthen includes a temperature indicating instrument 238 and an associatedcontrol device 240 for measuring the temperature of the water as itexits the feed pump 111 before it enters the PIP heat exchanger section122 and for giving an alarm 240 if the temperature is too high. If thetemperature exceeds the maximum operating temperature for the feed pump111, control device 241 will communicate with the burner managementsystem to trip the burner. The water then proceeds through the PIP heatexchanger section 122 and exits as previously described in relation toFIGS. 1A and 1B and then exits where its temperature and pressure aremeasured using pressure transmitting instrument 242 and temperaturesensor instrument 244, that each have control devices 246, 248.

Next, the water flows through the extended surface economizer 121. Atemperature indicating instrument 250 in the form of a thermocouple orresistance temperature detector measures the temperature of the fluegases exiting the extended surface economizer 121. Its associatedcontrol device 252 performs two functions. An alarm is generated via thePLC as an indication of excessive ash buildup. The second but primaryfunction of the temperature control device 252 is as an input to thesteam quality algorithm which will be elaborated upon later. The waterthen exits the extended surface economizer and flows back through thePIP heat exchanger as previously described. The temperature of the wateras it enters and exits the PIP heat exchanger is again measured bytemperature measuring instruments 254, 256 to make sure that itstemperature is within acceptable parameters as it enters and exits thePIP heat exchanger respectively. If not, the associated alarm devices258, 260 of the PLC are notified.

The water then flows through the bare tube section of the system 124 andexits toward the radiant section 126 where its pressure and temperatureare measured by instruments 262, 264 respectively and monitored by theirassociated control devices 266, 268 respectively. If these values areoutside of acceptable parameters, an alarm signal is generated from thePLC. The water then enters the radiant section 126 where it is heatedeven further to turn the majority of the water into steam. Thetemperature of the pipe/water in the radiant section is measured by atemperature measuring instrument 270 to see if its temperature exceeds amaximum value. The associated control device 272 signals and relays itto the PLC and triggers an alarm 272 if the maximum operating thresholdvalue is exceeded. If the temperature continues to rise above thesetpoint established in temperature control device 273, the burner willbe stopped to prevent possible damage to the radiant section 126 of thesystem 120. As the steam exits the heat generating system 120, itstarget quality is usually in the 80 to 90 percent range where it headstoward the delivery system 130.

Focusing on the burner 128, its operation and control in relation toother inputs to the PLC will be discussed in more detail later withrespect to FIG. 3A thru 3C. It should be noted that the flue gasescreated in the radiant section 126 travel up through the bare tubesection 124 and extended surface economizer section 121 until it reachesthe vent or flue found physically on top of the extended surfaceeconomizer where the oxygen content of the gases is analyzed by sensor274. The amount of oxygen content is relayed to the PLC through theassociated control device 276 if the oxygen content is too high or toolow. A low oxygen alarm 275 indicates incomplete combustion and notenough air is being sent to the burner. Too much oxygen contentindicates an error in the analyzer. When there is excess fuel or whennot enough oxygen is being sent to the burner as required perstoichiometric predictions, small pockets of unburned fuel may collectwithin the furnace 126 that auto-ignite randomly which is undesirable.Accordingly, it is desirable to run the combustion with a 3-4% oxygenrich mixture. Also, as alluded to above, the stack temperature is takenby a thermocouple 250 to make sure it does not exceed a maximum valueand this information is relayed to the control device 252 and the PLC.

The steam and water delivery system 130 will now be described withreference to FIG. 2E1, 2E2 and 2E3 where it is illustrated by anotherdetailed schematic. Focusing for now on FIG. 2E1, the steam/watermixture travels to a steam separator 278 that is part of the steamquality measuring subsystem 132 that takes a portion of the water fromthe mixture and sends it to a sample cooler 280 where it is cooled andits conductivity is measured and compared to the conductivity of theincoming feedwater. This allows the quality of the steam/water mixtureto be calculated. This is done manually on a periodic basis usingequipment and methods commonly known in the art such as a conductivitymeasurement instrument. This actual value is then compared to atheoretical value that is calculated using an algorithm programmed intothe PLC to be elaborated upon later that predicts and helps attain adesired steam quality based on measurements taken and controlled by thecontrol system. An adjustment is then made by entering a correctioncoefficient into the program done manually by the user each time thesteam quality is measured to correct for predictive error in thealgorithm or other inefficiencies in the apparatus. This is done using aGUI (graphical user interface) or HMI (human-machine interface) such asa touchscreen as is well known in the art but other devices and methodscould be used such as a keyboard, mouse, etc. A thorough discussion ofthis algorithm is forthcoming. It is also contemplated that this processcould be automated.

The steam quality measuring subsystem 132 provides an intermittent slipstream of the main flow path and the majority of the steam/water mixtureproceeds to flow toward the venting subsystem 134 (see FIGS. 2E1, 2E2and 2E3) down the main steam header supply pipe 285 that includes firstand second pressure safety valves 282 and 284 respectively, that vent toatmosphere if a pressure surge occurs that exceeds certain thresholds.Later, the steam/water mixture arrives at a vent pipe 286 that includesa pressure control valve 288 that can be selectively opened when desiredin conjunction with the closing of other valves in the delivery system130 in order to vent at least one of water and steam to a tank orreservoir as will be discussed in more detail later herein. There is avalve position indicating device 290 that is associated with this valve288 as well as a valve position demand signaling device 292 as well as acontrol device 293 within the PLC that is in communication with device292. Both the valve position indicating device 290 and its associatedcontroller 291as well as the control device 293 communicate with the PLCso that it knows when to open or close the valve and at what positionthe valve actually is located.

Along the main steam header pipe 285 there is a flow indicatinginstrument 294 (see FIG. 2E1) that is part of the steam injectionsubsystem 138 that includes an associated control device 295 thatmeasures the flow of the steam/water mixture to make sure that it is nottoo high or too low and sends that signal to the PLC. After that, thereis a main steam header pressure measuring device 298 (see FIG. 2E2) thatincludes an associated control device 281 that communicates with the PLCto show whether the pressure is too high or too low. At the same time,control signal device 281 is in communication via the PLC creating avalve position demand signal 283 that opens or closes the main headerpressure control valve 296 (see FIG. 2E3), the position of which isdetected and transmitted to the PLC through position indicatinginstrument 287 and an associated control instrument 289 (see FIG. 2E2).These devices and instruments also work together for opening and closingthe pressure control valve 288 for the venting line when desired. Thisarrangement and control logic allows the valves 296, 288 to operate intandem in a manner that will be discussed in more detail later.

Another temperature measurement instrument 251 that is part of the steaminjection subsystem 138 is found along the main steam header pipe 285that indicates through an associated control device 253 whether thetemperature of the steam/water mixture is still within an acceptablehigh and low range. If the temperature continues to rise to a very highlevel, the PLC will send a signal 255 to the burner management system toturn off the burner. The last measurement device found along the mainsteam header pipe is pressure transmitting instrument 297 (see FIG. 2E3)that includes an associated control device 299 that is in communicationwith the PLC and feedwater recirculation flow control valve 218 asalluded to above with reference to FIG. 2C. This valve 218 and mainsteam pressure control valve 296 work together to modify the feedwaterflow rate and injection pressure, which directly influence each other,to provide the desired pressure of the steam/water mixture to theinjection well while also maintaining a consistent pressure in the steamgenerating system 120. This cooperation between these valves and the PLCwill be discussed more thoroughly later.

Branching off the main steam header pipe 285 is the supply line 267 (seeFIG. 2E2) that diverts part of the steam/water mixture to the bleed-offsubsystem 136 for supplying auxiliary equipment with steam at a reducedpressure. A pressure control or flash valve 269 is provided that reducesthe pressure by approximately 90%. Associated actual valve indicatingdevice 207 and its associated controller 215, and valve position demandsignaling device 213 as well as pressure control device 217 are providedin similar fashion as has been described for other pressure and flowcontrol valves. Also, a steam pressure measuring instrument 219transmits a signal to the PLC which, through an algorithm or routine,sends a signal to the pressure control device 217 to the pressurecontrol or flash valve 269 to maintain pressure. Then a steam separator221 (see FIG. 2E3) removes the water from the mixture and sends it tothe feedwater preheater for the sake of conservation of energy to beginto warm up the feedwater. The remaining steam is sent to the oil burner128 for atomizing the fuel, to the feedwater preheater to conserveenergy and warm up the feedwater, and to the warm the fuel of the oilheater when heavy oil is being used.

It is to be understood that components used for the apparatus justdescribed are often commercially available and can be interchanged withsimilar devices known in the art depending on the application. Forexample, the instruments and devices described herein are mostlypneumatically powered by a system-wide air compressor but it iscontemplated that other devices powered by other methods or devices suchas hydraulics, electrical or mechanical could be employed. Likewise, thecontrol system could be altered using any devices or methods known inthe art suitable for implementing various methods for startup andcontinuous operation as will be described later herein. For example,other control systems could be used such as mechanical linkages,computer or hard-wired digital logic systems. Similarly, wires have beenused that convey a signal ranging from 4 mA to 20 mA but other systemscould be chosen. When using such a signal, 4 mA corresponds to a signalfor closing a device or minimizing a readout while a 20 mA signalcorresponds to a signal for opening a device or for maximizing a readoutand for analog applications, anything between these values is calibratedto create a proportional reading or control of a device. Of course,valve operations could be designed to operate in the opposite directionwith the same control signal.

FIGS. 3A, 3B and 3C show in a segmented fashion a detailed schematic ofthe inputs and outputs and related control system associated with burnerunit 128 that is designed to use multiple fuels including natural gas,#2 oil (diesel) and/or #6 oil (heavy oil) and/or any other gaseous orliquid fuel (best seen in FIG. 3A is a typical schematic of such aburner). For example, gas may be sent to the burner with its flow ratecontrolled by flow rate control valve 300 (see FIG. 3B). The flow ratemay be monitored using flow transmitting instrument signal 303 conveyedto the PLC. Natural gas supply instrument 302 transmits its signal tothe PLC to alarm if conditions or measurements are abnormally low orhigh. Both the valve and the flow measuring instrument are incommunication with control device 304. If not enough gas is being sentto the ignition system, then a demand signal 306 is increased, which inturn causes the valve to open. Similarly, other fuels can be usedseparately or in tandem with each other and be controlled in like mannerto what has just been described so that the amount of fuel, andtherefore, energy might be calculated in conjunction with the air flowrate. The air flow rate is measured using a flow element 308 (see top ofFIG. 3A). If more air is needed, then a control signal 310 is sent tothe fan or blower 129 by the controller 312, which in turn increases therate of rotation of the fan (see top of FIG. 3B). Likewise, the air flowcould be adjusted using devices or methods known in the art suitable forthis application.

An Atomizing media, such as steam that is received from the bleed-offsystem as has been described or compressed air is sent to the burner tomix with oil to atomize the oil and reduce its particle size to improveits combustion efficiency in the furnace (see FIG. 3C). Propane ornatural gas is also supplied for creating the pilot light for theburner. Excess oil not needed by the burner is returned to the oil tank(see bottom of FIG. 3A). Likewise other methods of atomizing the liquidfuels known in the art are suitable for this application.

Also, the control system may be able to sense when the feedwater rate isincreased or decreased and may adjust the burn rate accordingly. That isto say, the fuel and air rates would also being increased to compensatefor the increased feedwater flow rate in an attempt to maintain thedesired steam quality that is made by the steam generating system.

With reference to the architecture of the various systems that comprisevarious embodiments of the apparatus of this disclosure, a number ofprotocols, algorithms, processes, or methods may be employed for startupand normal continuous operation including those that follow. For sake ofconvenience and clarity for the reader, Table I is provided below thatshows a description of some of the devices/signals, signalinputs/outputs and alarm annunciators as well as their associatedreference numerals and I/O type for the control system. For this table,DI represents digital input, DO represents digital output, AI representsanalog input and AO represents analog output.

TABLE I I/O Ref. Type Numeral Description of Device/Signal DI 228Feedwater Pump Inlet Pressure Low Alarm/Device DI 204 Feedwater PumpHand Switch In Auto DI 206 Feedwater Pump Vibration High Alarm DI 208Feedwater Pump Drip Oil Tank Level Low Alarm DI 209 Feedwater PumpCrankcase Oil Tank Level Low Alarm DI 210 Feedwater Pump Run Confirm DO211 Feedwater Pump Start/Stop AI 207 Process Steam Pressure ControlValve Position AI 219 Process Steam Pressure AI 222 Feedwater FlowControl Valve Position AI 230 Feedwater Pump Outlet Pressure AI 234Feedwater Flow AI 238 Feedwater Pump Outlet Temperature AI 242 ExtendedSurface Economizer Feedwater Inlet Pressure AI 244 Extended SurfaceEconomizer Feedwater Inlet Temperature AI 250 Stack Temperature AI 251Main Steam Header Temperature AI 254 Extended Surface EconomizerFeedwater Outlet Temperature AI 256 Bare Tube Section Feedwater InletTemperature AI 262 Radiant Section Feedwater Inlet Pressure AI 264Radiant Section Feedwater Inlet Temperature AI 270 Radiant Section SteamOutlet Temperature AI 274 Flue Gas Oxygen AI 287 Main Steam HeaderPressure Control Valve Position AI 290 Main Steam Startup Valve PositionAI 294 Main Header Steam Flow AI 297 Injection Steam Pressure AO 213Process Steam Pressure Control Valve Demand AO 225 Feedwater FlowControl Valve Demand AO 283 Main Steam Pressure Control Valve Demand AO292 Startup Valve Demand

As depicted by FIG. 4 in generalized steps and sub-process steps, astartup algorithm or routine 400 may be implemented by the controlsystem and executed to perform the following method for starting theapparatus. First, the following conditions should be satisfied beforethe feedwater pump 111 start command is issued and the run contact isenergized. The motor trip alarm should have been reset (step 402). Oneof the booster pumps that provides flow to the feedwater pump should berunning (step 404) which is proven if the feedwater pump inlet pressureis not too low (step 406). The hand switch of the feedwater pump shouldbe in the auto position (step 402). Also, the feedwater pump outletpressure must not be too high, the feedwater pump outlet temperaturemust not be too high (step 408), the feedwater pump vibration switchmust be reset, and the feedwater pump drip oil tank level must not betoo low (step 410). Also, the air instrument pressure must not be toolow (step 412) or instruments must be otherwise energized. Finally, thefeedwater pump crankcase oil level must not be too low (step 414). Ofcourse, these conditions may vary depending on the selection of the pumpand the overall design of the system. Accordingly, the algorithm orroutine and associated method in its broadest interpretation may reduceall these conditions into a go or no go situation, that is to say, is itpermissible for the feedwater pump to run (step 413). If so, then thealgorithm or routine 400 or method should proceed to the next step.

At a minimum in certain embodiments, it is desirable that the downstreamtemperature and pressure of the water from the pump be not too high, andthat the instrumentation for the apparatus be powered. For example, thevalves, actuators and other devices should be supplied with enough airor hydraulic pressure, enough electricity or mechanical force, or otherform of energy depending on the device to work properly. If at leastminimum of these conditions is satisfied for these embodiments, then itis permissible for the pump to be energized.

Provided that it is permissible for the feedwater pump to run, a signalis sent to the feedwater pump to turn it on and the starter contactsends a signal back to the controller confirming that pump is in factrunning. If this contact is not made when the run confirmation timerexpires, a feedwater pump failed to start alarm is annunciated and therun contact is de-energized. If the pump inlet pressure switch opens,the feedwater pump will trip and a feedwater pump low inlet pressurealarm is annunciated. If the feedwater outlet pressure exceeds the highlimit, the feedwater pump will trip and a feedwater pump outlet pressurehigh alarm is annunciated. If the feedwater outlet temperature exceedsthe high limit, the feedwater pump will trip and a feedwater pump outlettemperature high alarm is annunciated. Any one of these alarms orwarnings can lead to a shutdown of the feedwater pump after the pump hasbeen turned on.

If the instrument air pressure (not shown in the schematics) or otherpowering system when other types of instruments are used is notproviding the necessary energy, the feedwater pump will trip and aninstrument low air pressure alarm or other similar type of alarm will beannunciated. If the pump vibration switch opens, the feedwater pump highvibration alarm will be annunciated and since the switch is alsohardwired in series with the pump starter contactor, the feedwater pumpwill trip. Likewise, if the feedwater pump crankcase oil level switchopens, the feedwater pump low crankcase oil level alarm will beannunciated and since the switch is also hardwired in series with thepump starter contactor, the feedwater pump will trip. Again, any one ofthese alarms or warnings can lead to a shutdown of the feedwater pumpafter it has been turned on.

If the feedwater pump drip oil tank level switch opens, a feedwater pumpdrip oil tank low level alarm will be annunciated and a one hour timerwill start. In order to stop the running of this timer, the operatorneeds to reset the alarm by pushing the reset button after refilling thedrip oil tank. If the feedwater pump drip oil tank low level switchstays open for more than one continuous hour, the feedwater pump willtrip. Of course, this can occur at any time during the operation of thepump.

Assuming that the feedwater pump is running, then the start routine 400,method or associated algorithm proceeds to the next step as follows. Thestartup valve 288 is opened an appropriate amount to vent steam andwater directly from the main steam header pipe 285 to the vent tank orreservoir (step 415) until it has been determined that the steam/watermixture is suitable (step 416) to be sent toward the injection well orother desired destination (step 418). At the same time the main headerpressure control valve 296 is closed an appropriate amount or entirelyuntil the desired parameters have been achieved. This can all be donedependent on parameters input by a user or that were previouslyprogrammed into the controller. Of course, any of these steps of thismethod or any other discussed herein may in certain cases be performedin a different order or may be omitted depending on the application anddesign of the apparatus. Consequently, the flowchart in FIG. 4 isdepicted in broad steps and should not be construed as the soleembodiment of this disclosure. Additionally, more steps could be addedto this routine or method or any other routine or method discussedherein.

Turning now to FIG. 5A, another method or routine 500 that can beimplemented by the control system and executed during normal operationincludes the following steps. The injection pressure at the injectionwell or other desired location is determined to be within acceptableparameters (step 502). If not, then the feedwater flow rate is adjusted(step 504) as well as the burn rate (step 506) of the burner of thesteam generating system. Then, it is determined whether the feedwaterflow rate and pump discharge pressure are within acceptable parameters(step 508). If not, then the feedwater flow rate is adjusted (step 510).This method was alluded to above with respect to the maintenance of theinjection pressure using the recirculation feedwater flow rate controlvalve 218.

Referring to FIG. 5B, sub-processes or subroutines and their steps areshown for determining whether the injection pressure is withinacceptable parameters, for adjusting the feedwater flow rate and foradjusting the burn rate. In one embodiment, a desired setting for theinjection steam pressure is placed into the computer such as by the uservia an input device or preprogrammed into the PLC. The injection steampressure is then measured. If the injection steam pressure is too low ascompared to the desired setting (step 512), then the recirculationfeedwater flow rate control valve is closed an appropriate amount (step514). If the injection steam pressure is too high as compared to thedesired setting (step 516), then the recirculation feedwater flow ratecontrol valve is opened an appropriate amount (step 518). This can beautomated using the PLC since all the necessary components arecommunicating with the PLC and therefore with each other. This can beconsidered the first control loop 520 for maintaining the desired mainsteam header pressure. Naturally, steps 522 and 524 require that theburn rate be raised or lowered respectively to match the increase ordecrease in the flow rate in an effort to maintain the desired steamquality.

There can also be a secondary control loop 526 that is also depicted byFIG. 5B based on the feedwater flow rate. It would comprise thefollowing steps: measuring the feedwater flow rate, inputting a maximumvalue for the flow rate into the control system, which may be done inany manner including manually or by programming, and comparing thefeedwater flow rate to the maximum value for the flow rate. If thefeedwater flow rate is above the threshold value (step 528), then thesecond control loop takes precedence over the first control loop and theflow rate is decreased (step 530) even if the desired injection steampressure has not been reached. On the other hand, if the flow rate istoo low (step 532), then the flow rate may be increased (step 534) aslong as the pump discharge pressure is not too high (step 533).

In certain embodiments as shown by FIG. 5C, either the controller linkedto the feedwater flow rate or to the injection steam pressure controllercan be placed in manual or automatic mode. This yields four separatescenarios with the typical scenario being the one where both controlsare placed in automatic mode (step 536).

This first scenario allows the injection steam pressure controller tocontrol the feedwater flow rate until the desired pressure has beenreached. This may involve the steps of inputting the desired injectionpressure range into the control system (step 538). Then, the injectionpressure and feedwater flow rate are measured (step 540). This continuesuntil the feedwater flow rate or the injection pressure are not withindesired ranges (step 542). Then, the recirculation feedwater flow ratecontrol valve is opened or closed as necessary to obtain the desiredinjection pressure range (step 544). The output of the feedwater flowrate controller is at and remains at 0% until the flow rate approachesthe high flow limit, such as when it exceeds the design conditions ofthe steam generator, at which time its output is greater than the outputof the injection steam pressure controller and controls therecirculation feedwater flow rate. The high feedwater flow rate limit issometimes automatically set when the injection steam pressure controlleris placed into automatic mode to avoid an operator forgetting to set theappropriate limit. Typically, these control loops can only be put intoautomatic if the feedwater pump is running. If the feedwater pump stopsfor any reason including those related to the conditions necessary tostart the pump discussed with reference to FIG. 4 above, both thefeedwater flow rate controller and injection steam pressure controllerare placed into manual mode and the output is placed to 100% so at leasta minimal amount of water flows to the steam generating system helpingto keep its components from overheating. It is to be understood that asetpoint for any value whether it be flow rate, pressure or temperaturedisclosed herein may include a range or single setpoint so the termrange or setpoint should be considered equivalents of each other.

As mentioned previously when looking at FIG. 2C, a position transmitter222 provides position feedback from the feedwater flow rate controlvalve 218 (see step 546 of FIG. 5C). If the actual position deviatesmore than 5% from the valve position demand signal 225 (step 548), afeedwater flow rate control valve position deviation alarm isannunciated to alert that there may be a problem with the valve (step550). These steps of measuring a valve's position, comparing it to adesired position, and annunciating an alarm if the deviation is toogreat may be used in conjunction with any valve that includes theappropriate instruments and controls.

In the second scenario, both the feedwater flow rate controller and theinjection steam pressure controller are both placed in manual mode sothey need to track each other. The output buttons on the injection steampressure controller are not visible to the operator when bothcontrollers are in manual mode. Consequently, the operator only hasaccess to manipulate the output of the feedwater flow rate controller(shown as 236 in FIG. 2C) and the logic of the PLC tracks this andmatches it on the injection steam pressure controller (shown as pressurecontroller 299 in FIG. 2E3).

In the third scenario, the feedwater flow rate controller is inautomatic mode and the injection steam pressure controller is placed inmanual mode. In such a case, the recirculation feedwater flow ratecontrol valve is always opened or closed to the higher of eithercontroller output. If the output of the injection steam pressurecontroller is set to 100%, then the output of the feedwater flow ratecontroller has no effect, since the control valve will always stay at100%. In order for the feedwater flow rate controller to exclusivelycontrol the valve when it is in automatic mode, the setting for theinjection steam pressure controller has to be 0%.

In the fourth scenario, the feedwater flow rate controller is put intomanual mode and the injection steam pressure controller is placed intoautomatic mode. The result is the same as the second scenario exceptthat the output of the feedwater flow rate controller must be set to 0%in order for the injection steam pressure controller to be exclusivelyin control.

While scenarios three and four are used from time to time to manuallycontrol the steam injection pressure or feedwater flow raterespectively, the first scenario is the one typically used and involvesplacing both the feedwater flow rate controller and the injection steampressure controller into automatic mode. The second scenario isdiscouraged as it does not take advantage of the control system and itslogic.

FIG. 6 depicts the steps of another routine 600 or method that can beimplemented and executed by the control system. This routine 600 is wellsuited once the startup routine has been accomplished and normaloperation has ensued. Once the steam/water mixture is determined to beof suitable quality, the main header pressure control valve 296 isopened and the startup valve 288 is closed an appropriate amount tomaintain the main steam header pressure at an operator selected orpreprogrammed level. Also, excess steam pressure that may arise duringsome sort of event, excursion or surge can be vented using the vent orstartup valve 288.

Specifically, the main steam header pressure 298 is controlled by abackpressure control valve 296 in the main steam line 285 (see FIGS. 2E2and 2E3). First, it is determined whether the pressure in the main steamheader pipe or line is within acceptable parameters (step 612 in FIG.6). A possible sub-process or subroutine for this may include thefollowing steps. A desired pressure is input into the main steam headerpressure controller 287 (step 604 in FIG. 6) by any method includingmanually or by programming. This controller can only be put intoautomatic mode (step 602) if the feedwater pump 111 is running and theburner 128 is released for modulation, that is to say, it is in normaloperation mode. The pressure is then measured and compared to thedesired value (step 614).

Referring back to the main process, if the measured pressure is greaterthan the desired value, then the steam and/or water mixture is sent tothe venting reservoir (step 616). If either the feedwater pump stops(step 606) or the burner is shut off (step 608), this controller isautomatically switched to manual (step 610) and the output is pulsed tozero and backpressure control valve 296 closes so that some pressure ismaintained within the steam generation system. Once more, the sameconditions that have been discussed as necessary to start the feedwaterpump could also cause the pump to stop if they are not satisfied. Also,a position transmitter 287 provides position feedback from the mainsteam header pressure control valve 296. If the actual valve positiondeviates more than 5% from the valve position demand signal 283, a mainsteam header pressure control valve position deviation alarm isannunciated. Lastly, the main steam header pipe may be provided withpressure safety valves 282, 284. This method may also include the stepof determining whether the pressure in the main steam header pipe isgreater than the designed release pressure of one of the safety valves(step 618). If so, then one of the pressure safety valves opens. Itshould be noted that this may be done without any signal from thecontrol system as such valves are usually constructed with a mechanicalspring that keeps the valve closed until a setpoint steam pressureovercomes the spring pressure opening the valve (step 620).

Yet another routine, algorithm or associated method that can beimplemented by the control system during normal operation comprises thefollowing steps. First, the pressure setting for the vent pressurecontrol valve or startup valve 288 is set at a threshold value by anysuitable method including manually or via a program so that its value isslightly higher than main steam header pressure controller 281 setting.If the pressure exceeds this threshold value, then the vent pressurecontrol valve 288 opens up an appropriate amount to allow excess steampressure to escape to the venting reservoir. Thus, the valve providesboth the functions of an excess steam pressure relief valve when thereis a surge or excursion in the main steam header pressure or injectionsteam pressure during startup and normal operation. In an embodiment,the controller associated with the startup valve 288 is automaticallyplaced in automatic mode by the PLC logic when the feedwater pump isstarted. If the feedwater pump stops, then this controller 293 isautomatically switched to manual and the output is pulsed to zero andthe startup valve 288 is closed as it is desired to maintain somepressure and water in the steam generation system to help preventoverheating. A position transmitter 290 tells the control system theposition of the valve 288 and if the actual position deviates more than5% from the valve position demand signal 292, a startup or vent valveposition deviation alarm is annunciated.

Turning attention now to the bleed-off subsystem, a process steamcontrol valve 269 is used to reduce the steam pressure from the mainsteam header pressure to a suitable pressure for the process steam thatis sent to the fuel oil heater, feedwater heater, burner atomizing steamand soot blower (not shown in the figures). The following method andassociated algorithm may be employed during normal operation. First, adesired pressure is placed in the process steam pressure controller 217.The pressure is then measured using pressure measuring device 219. Ifthe pressure is not within acceptable parameters, then the valve isopened or closed as needed to place the pressure in the desired range.In an embodiment, this controller can only be placed in automatic modeif the feedwater pump is running and the burner has been released formodulation, that is to say, it has been cleared by the control systemfor normal operation. If the feedwater pump stops or the burner is shutoff, this controller is automatically switched to manual and the outputis pulsed to zero, and the valve is closed, as it is desired to maintainsome water pressure in the steam generation and delivery systems. Avalve position transmitter 207 provides position feedback from theprocess steam pressure control valve 269. If the actual valve positiondeviates more than 5% from the valve position demand signal 213, aprocess steam pressure control valve position deviation alarm isannunciated.

Yet another routine 700 (see FIG. 7A), algorithm or method that can beimplemented by the control system provides the following process foradjusting the burner firing rate to achieve a desired steam qualitybeing sent to the injection well or other desired destination from thesteam generating system. First, the temperature of the water supplied bythe feedwater system to the steam generation system as well as its flowrate and enthalpy are determined (step 714) by any device or methodknown in the art or that will be devised in the art. This step may beachieved using sub-steps of a sub-process or subroutine including thefollowing. If the feedwater temperature signal quality input to thecontrol system is within acceptable parameters (step 702), then thefeedwater enthalpy is calculated by subtracting a value of thirty-twofrom the measured temperature in degrees F. to get the feedwaterenthalpy in BTU/lb (step 704). If the temperature's electronic signalquality is bad, then the temperature is assumed to be about 200 degreesF. and the feedwater enthalpy is estimated to be 168 BTU/lb (step 706).It is contemplated that the enthalpy of the water could be estimatedsome other way such as using a table since the system is capable ofmeasuring the temperature and pressure of the water.

Second, as best shown by FIGS. 7A and 7B, the algorithm computes orestimates the target steam enthalpy (step 710) based on the operator settarget percent value for the steam quality that has been entered intothe control system using an input device (step 708) such as a HMI andthe current main steam header pressure instrument 298 signal using thefollowing equation: Target Steam Enthalpy=(Target Steam QualityPercent/100)*(Current Enthalpy of the Steam Vapor−Current Enthalpy ofthe Steam Liquid))+Current Enthalpy of the Steam Liquid (step 716 ofFIG. 7B) where steam quality is initially expressed as a percent. Thecurrent steam header vapor and liquid enthalpies associated with themain steam header pressure are retrieved from look-up tables that arebased on ASME steam tables and are stored in a database. In oneembodiment, the tables cover a pressure range from 0 to 1800 psig withan enthalpy value for every 100 psi increment (step 718 of FIG. 7B). Theprogram may determine if the pressure is located between those listed inthe table (step 720 of FIG. 7B) and may automatically interpolate forpressures found between these 100 psi listed increments (step 722). Itis to be understood that similar programs known in the art may be usedto determine the steam vapor and steam liquid enthalpies. The pressureof the steam/water mixture is measured as it exits the steam generationsystem in a manner that has already been described. It is contemplatedthat the desired steam quality could be set by any known method ordevice known in the art or that will be devised in the art (step 712 ofFIG. 7A) such as by preprogramming without the need of a user to input avalue into the control system.

The next step (step 724 of FIG. 7A) includes calculating the amount ofheat that is required to be added to each pound of feedwater in order toachieve the desired steam quality. This may be accomplished bysubtracting the feedwater enthalpy from the target steam enthalpy, bothof which have been calculated as discussed above. This may berepresented by the following equation: Heat Required=Target SteamEnthalpy−Feedwater Enthalpy.

However, the amount of heat that must be generated and put into thewater by the steam generating system is affected by the efficiency ofthe steam generating system, especially that of the boiler whichincludes the radiant section, bare tube section and the extended surfaceeconomizer section. The boiler efficiency can be estimated as follows asbest seen in FIG. 7C. First, the flue gas oxygen level signal andcontent are measured as has been previously described to determine if itis within an acceptable range (step 726). In one embodiment, thetransmitted signal to the control system from 274 will be between 3.8and 21.0 mA. If it is within this range, then the actual correspondingoxygen content is used in the calculation involving the boilerefficiency (step 728). If it is outside this range, then the flue gasoxygen content is assumed to be 3% (step 730). Similarly, the stacktemperature signal is measured, and if its signal is within acceptableparameters (step 732), the actual temperature provided by thethermocouple or other measuring instrument is used in the calculation(step 734). In one embodiment, this range is anything that falls withinthese signal limits. If the measured temperature is outside thepermissible range, then a temperature of 480 degrees F. is assumed (step736). Also, the type of fuel burned in the burner is considered (step738). If natural gas is used as fuel, then an equation is derived from amatrix of efficiency numbers obtained from running a boiler heat balanceprogram for various flue gas oxygen values and stack temperatures (step740). The calculation may be made using the equation as follows: BoilerEfficiency=Boiler Specific Factor+(20.95/(20.95−Measured Flue Gas OxygenPercent)*0.02153*(350−Measured Stack Temperature))−Radiation Loss. (Seestep 742).

Specifically, the equation given above is determined by fitting a curveto experimental data where the specific type of unit and its inherentinefficiencies are taken into account to develop the Boiler SpecificFactor above as well as the effects that the Flue Gas Oxygen Content andthe Stack Temperature have on the unit's efficiency while using naturalgas. In one embodiment, the Radiation Loss can be assumed to be 1% andis stored in the database. Alternatively, if #6 oil is used, then theequation is adjusted as follows: Boiler Efficiency=Boiler SpecificFactor+(20.95/(20.95−Measured Flue Gas OxygenPercent)*0.02117*(350−Measured Stack Temperature))−Radiation Loss. If #2oil is chosen to be burned, then 0.61% is subtracted from thiscalculation to get the Boiler Efficiency for #2 oil.

Next, it is determined if the calculated efficiency is within the rangeof 60 to 95% (step 744). If the calculated boiler efficiency number isgreater than 95%, then the algorithm assumes that the boiler efficiencyunit is 95%. If the calculated boiler efficiency number is less than60%, then the algorithm assumes that the boiler efficiency is 60% (step746). Otherwise, the boiler efficiency is set to the calculated valuefound between 60 and 95% (step 748).

Once the boiler efficiency has been determined as well as the requiredheat input, then the Specific Gross Heat Input per pound of feedwatercan be calculated by dividing the required heat input (step 724) by theappropriate boiler efficiency (step 750). This step can be representedby the following equation: Specific Gross Heat Input=Heat Required/Boiler Efficiency.

Turning back to FIG. 7A, the Gross Heat Input Rate is calculated inthousands of BTU/hr by multiplying the specific gross heat input justdiscussed by the measured feedwater flow rate (step 752). This step isrepresented by the following equation: Gross Heat InputRate=2,205*Feedwater Flow Rate*Specific Gross Heat Input/1000 where theFeedwater Flow Rate is calculated using mt/h (metric tons per hour) andthe conversion factor is built into the equation.

Once the Gross Heat Input Rate is determined, then an Adjusted GrossHeat Input Rate needs to be calculated depending on which fuel is beingused in order to express in percent what portion of the burner heatinput should be used (see FIG. 7D). If natural gas is being used (step756), then a higher heating value is used (often provided by theoperator through the input device such as a HMI) as well as a NaturalGas Load Factor that converts to the percent burner load that is storedin the database. The following equation can be used: Adjusted Gross HeatInput Rate=1000*Gross Heat Input Rate/Gas Higher Heating Value*NaturalGas Load Factor. The Natural Gas Load Factor is stored in a database andconverts from SCFH (standard cubic feet per hour) to a percent(dimensionless number) of the burner load (see step 758).

Similarly, if #2 oil is used (step 760), the Adjusted Gross Heat InputRate=1000/60*Gross Heat Input Rate/#2 Oil Higher Heating Value*#2 OilLoad Factor where this factor is stored in a database and converts fromgpm to a percent of the burner load (dimensionless number) (see step762). This factor is often fixed at 30.92 (step 764).

Finally, a similar step can be used when #6 oil is being used (step766). In such a case, the following equation is used: Adjusted GrossHeat Input Rate=1000/60*Gross Heat Input Rate/#6 Oil Higher HeatingValue*#6 Oil Load Factor where this factor is stored in a database andconverts gpm to a percent of the burner load (step 768). This factor isoften fixed at 32.26 (step 770).

Other gaseous or liquid fuel can be fired in the burner. Similarcalculations and programming can be done.

Once the Adjusted Gross Heat Input Rate is determined, an additionalfactor may be multiplied to get the desired percent burner load. Onceknown, the PLC may automatically adjust the firing rate (step 754 ofFIG. 7A) until the stack temperature and flue gas oxygen content, (andas a result the calculated boiler efficiency) change to match therequired burner heat input necessary to match the desired steam quality.As mentioned earlier, the actual sampled steam quality may be comparedto the predicted or desired steam quality. Any difference can be used tocreate a correction factor to compensate for inefficiencies in thesystem and error in the algorithm. So, if it is predicted that the steamquality would be 90% but it is in fact 88%, then a correction factor canbe entered in the control system for adjusting for this 2% error. Thiswould increase the burn rate by an appropriate amount to obtain thedesired 90% steam quality.

In addition, the control system may use the measured steam flow in mainsteam header pipe to estimate what the current quality of the steam is.During startup, the feedwater flow rate is measured and the steam issampled to determine its quality and a curve is generated throughout theoperating range plotting pressure differential across the steam flowelement versus quality as measured. From this curve, an estimated steamquality is displayed on the GUI or HMI and allows the operator to havean estimation of whether the steam quality is within desired parameters.If there is a difference between the estimate and actual tested steamquality, then an adjustment may be made to the burn rate. As mentionedpreviously, a correction coefficient can be entered into the controlsystem to help correct for predictive error with respect to thisalgorithm so that it is more accurate and adjust the burner rate asneeded. This error may be a result of or related to energy losses withinthe system and is typical with such systems. Nevertheless, it isrecommended that the operator periodically check the actual steamquality using quantitative steam quality measuring instruments. Thisprocess could also be automated so that the algorithm self correctsitself on regular intervals.

Also, this process may be changed depending on the amount of accuracyneeded for a particular application. Therefore, one or more of thevariables just described may be omitted or substituted for or anadditional variable may even be added depending on the situation. It iscontemplated that this algorithm and associated process could be thusvaried as long as some sort of model is used that takes intoconsideration the heat balance of the inputs and outputs of the steamgenerating system. Furthermore, the flow rates of the fuels and air maybe linked so that their individual control is rendered unnecessary. Forexample, a mechanical control may link the fuel flow rate to the airflow rate such as the use of linkages or this could be doneelectronically.

The GUI or HMI of the control system may provide graphical informationon the following process parameters including, the radiant section tubemetal temperature 270, the main steam header temperature 251, feedwaterpump outlet pressure 230, feedwater pump outlet temperature 238,extended surface economizer feedwater inlet pressure 242, extendedsurface economizer feedwater inlet temperature 244, extended surfaceeconomizer feedwater outlet temperature 254, bare tube section feedwaterinlet temperature 256, radiant section feedwater inlet pressure 262,radiant section feedwater inlet temperature 264, and stack temperature250 However, it is contemplated that more or less parameters could bedisplayed and/or available for input by a user through the GUI or HMI asdesired depending on the application.

Specifically, a control system that is used with the apparatus toimplement any of the methods discussed herein may include an inputdevice that may include any number of devices or methods currently usedor that will be devised in the art such as a keyboard, a mouse, atouchscreen, voice recognition, etc. Likewise, a number of outputdevices may be used that includes those currently used or that will bedevised in the art such as a display screen, flashing lights or othervisual displays or cues, audible alarms, etc. Furthermore, variouscontrol systems may be employed including a PLC, a distributed controlsystem (DCS), a gate array logic system, a mechanical system includingthose that use mechanical linkages, a hard wired logic system, amicroprocessor, a microcontroller, a PC that includes customizedsoftware that is configured to execute an algorithm and/or associatedmethod, etc. It is further contemplated that any of the routines,algorithms, methods or processes described herein may be accomplishedabsent a formal control system such as may be the case when one or moreoperators are acting in concert. For any routine, process or methoddisclosed herein, the algorithm, processor-executable code orinstructions may be stored in the PLC or in the memory of the controlsystem for execution on the PLC or the processor to perform theoperation, routine, process or method. Furthermore, the display languagecan be English or any other desired language.

In an embodiment of the apparatus that has just been described, it hasbeen possible to optimize the quality of the steam with little variance,allowing more heat to be effectively pumped into an injection well,raising the number of units of oil produced from an oil well per unitheat put into a steam injection well. Put into other terms, more oil isultimately produced for the money invested in making the steam and watermixture. In one embodiment, the feedwater supply coming into thefeedwater pump as shown in FIG. 2C satisfies the following conditions:the minimum pump inlet pressure is 50 psig, the maximum inlet pressureis 150 psig, the minimum inlet temperature is 60 degrees F., the desiredor normal temperature is 190 degrees F., the maximum inlet temperatureis 212 degrees F., minimum flow rate is 16 gallons per minute, thedesired or normal flow rate is 48 gallons per minute and the maximumflow rate is 57 gallons per minute. The feedwater pump motor may be madeby TECO WESTINGHOUSE and have the following specifications: one hundredhorsepower, 480 VAC with three phase at 60 Hz, 1200 RPM and it may betotally enclosed and fan cooled. The pump itself may be made by NATIONALOILWELL under model #1100-3M and it may include the followingspecifications: a design or preferred allowable pressure output of 1742psig, a maximum allowable pressure output of 2295 psig, a outputtemperature of 200 degrees F., a design or preferred allowable outputflow rate of 48 gallons per minute and a maximum allowable output flowrate of 57 gallons per minute.

Looking at the steam generation system of FIG. 2D, the steam generatoris cable of producing a heat output of 25.0 MMBTU per hour, includes adesign pressure of 1760 psig and is designed, fabricated and stamped inaccordance with ASME Boiler and Pressure Vessel Code Section I, LatestEdition.

Finally, some of the specifications for the equipment used in anembodiment of the delivery system such as shown by FIG. 2E will bediscussed. The steam separator that is used in conjunction with thebleed-off subsystem may be made by SPIRAX SARCO under model #4 inch SC4Special. It may be made using SA-106 GR. B steel, maximum allowableworking conditions of 300 psig and 650 degrees F., and the associatedinlet and outlet connections are made using 4 inch Class 300 RF flanges.A separate steam separator may be used in conjunction with the steamquality measuring subsystem that is installed in or as a side stream ofthe main steam header supply pipe. A device known in the art as a samplecooler is used to cool the steam sample to enable steam sample analysis.The steam quality measuring subsystem may be supplied with a shelldesign pressure of 285 psig, a cooling water design flow rate of 5gallons per minute, and a stainless steel coil design pressure of 3500psig.

The outputs from the delivery system are as follows: the normalinjection pressure to a steam injection well is 1500 psig, the maximumdesirable design pressure is 1760 psig, the normal temperature is 598degrees F., the maximum desirable design temperature is 619 degrees F.,the normal flow rate is 24,000 lb per hour, the maximum allowable flowrate is 24,314 lb per hour and the desired steam quality may range from0 to 90% but is in fact often within 80-90%. The output to the blowdowntank or venting reservoir includes a design pressure of 300 psig, adesign temperature of 619 degrees F., and a design flow rate of 24,000lb per hour. The output of condensed water to the feedwater heaterincludes a design pressure of 250 psig, design temperature of 406degrees F., and a design flow rate of 2,100 lbs per hour. The output ofsteam to the fuel oil heater includes a design pressure of 150 psig, adesign temperature of 375 degrees F., and a design flow rate of 200 lbper hour. The output of steam to the feedwater heater includes a designpressure of 150 psig, a design temperature of 375 degrees F., and adesign flow rate of 3,040 lb per hour. Lastly, the output of atomizingsteam to the oil burner includes a design pressure of 150 psig, a designtemperature of 375 degrees F., and a design flow rate of 200 lb perhour.

The control system and the present disclose of certain embodiments arenot to be construed to any system, inputs, or outputs or valuesdisclosed herein but is suitable for many different combinations ofequipment and for various design parameters, operating conditions andspecifications. Thus, the claims should not be limited to any specificembodiment disclosed herein.

One should note that conditional language, such as, among others, “can,”“could,” “might,” or “may,” unless specifically stated otherwise, orotherwise understood within the context as used, is generally intendedto convey that certain embodiments include, while other embodiments donot include, certain features, elements and/or steps. Thus, suchconditional language is not generally intended to imply that features,elements and/or steps are in any way required for one or more particularembodiments or that one or more particular embodiments necessarilyinclude logic for deciding, with or without user input or prompting,whether these features, elements and/or steps are included or are to beperformed in any particular embodiment.

It should be emphasized that the above-described embodiments are merelypossible examples of implementations, merely set forth for a clearunderstanding of the principles of the present disclosure. The logicalsteps, functions or operations described herein as part of a routine,process, or method may be implemented (1) as a sequence ofprocessor-implemented acts, software modules or portions of code runningon the PLC or other processor of the control system, or other computingsystem and/or (2) as interconnected machine logic circuits or circuitmodules within the apparatus 100 and associated control system(s). Theimplementation is a matter of choice dependent on the performance andother requirements of the system. Alternate implementations are includedin which steps, operations or functions may not be included or executedat all, may be executed out of order from that shown or discussed,including substantially concurrently or in reverse order, depending onthe functionality involved, as would be understood by those reasonablyskilled in the art of the present disclosure.

Any process descriptions or blocks in flow diagrams should be understoodas representing modules, segments, or portions of code which include oneor more executable instructions for implementing specific logicalfunctions or steps in the process, and alternate implementations areincluded in which functions may not be included or executed at all, maybe executed out of order from that shown or discussed, includingsubstantially concurrently or in reverse order, depending on thefunctionality involved, as would be understood by those reasonablyskilled in the art of the present disclosure. Many variations andmodifications may be made to the above-described embodiment(s) withoutdeparting substantially from the spirit and principles of the presentdisclosure. Further, the scope of the present disclosure is intended tocover any and all combinations and sub-combinations of all elements,features, and aspects discussed above. All such modifications andvariations are intended to be included herein within the scope of thepresent disclosure, and all possible claims to individual aspects orcombinations of elements or steps are intended to be supported by thepresent disclosure.

That which is claimed is:
 1. A method of starting up an apparatuscapable of producing at least one of water and steam of varying quality,the apparatus including a feedwater supply system that includes afeedwater pump, a steam generation system and a delivery system thatincludes a main steam header pipe that runs from the steam generationsystem to a destination, and a vent pipe that branches from the mainsteam header pipe and that runs to a venting reservoir, the methodcomprising the following steps: determining whether it is permissiblefor the feedwater pump to run; and sending at least one of water andsteam to the venting reservoir.
 2. The method of claim 1, which furthercomprises the step of determining whether a quality of at least one ofwater and steam is within acceptable parameters.
 3. The method of claim2, wherein the step of determining whether the quality of the at leastone of water and steam to be within acceptable parameters results in adetermination that the quality is not within acceptable parameters, themethod further comprising the step of sending at least one of water andsteam to the venting reservoir.
 4. The method of claim 2, wherein thestep of determining whether the quality of at least one of water andsteam is within acceptable parameters results in a determination thatthe quality is within acceptable parameters, the method furthercomprising of sending at least one of water and steam to a desireddestination.
 5. The method of claim 1, wherein the step of determiningwhether it is permissible for the feedwater pump to run occurs before atleast one of water and steam is sent to the venting reservoir.
 6. Themethod of claim 1, wherein the step of determining whether it ispermissible for the feedwater pump to run includes the step ofdetermining that a feedwater inlet pressure is not too low.
 7. Themethod of claim 1, wherein the apparatus further includes instrumentsand devices that are energized by a power supply and wherein the step ofdetermining whether it is permissible for the feedwater pump to runincludes the step of determining whether the instruments and the devicesare energized by the power supply.
 8. The method of claim 7, wherein theinstruments and the devices are energized by pressurized air that issupplied by an air compressor.
 9. The method of claim 1, wherein thefeedwater pump includes a crankcase for holding oil and the step ofdetermining whether it is permissible for the feedwater pump to runincludes the step of determining whether an oil level in the crankcaseis too low.
 10. The method of claim 1, wherein the feedwater supplysystem also includes a booster pump and step of determining whether itis permissible for the feedwater pump to run includes a step ofdetermining whether the booster pump is running.
 11. The method of claim1, wherein the feedwater supply system also includes a motor trip alarmand the feedwater pump includes a hand switch that is capable of beingswitched from off to automatic operation modes and wherein the step ofdetermining whether it is permissible for the feedwater pump to runincludes the step of determining whether the motor trip alarm has beenreset and the step of determining whether the hand switch has beenplaced into the automatic operation mode.
 12. The method of claim 1,wherein the step of determining whether it is permissible for thefeedwater pump to run includes a step of determining whether a feedwaterpump outlet pressure and an outlet temperature are too high.
 13. Themethod of claim 1, wherein the feedwater pump includes an oil tank and avibration switch and wherein the step of determining whether it ispermissible for the feedwater pump to run includes the steps ofdetermining whether an oil level in the oil tank is too low anddetermining whether the vibration switch has been reset.
 14. The methodof claim 1, wherein the apparatus further includes a plurality ofinstruments and devices and a control system that is operativelyassociated or in communication with the instruments and devices.
 15. Themethod of claim 14, wherein the devices include a valve that isoperatively associated with the main steam header pipe and another valvethat is operatively associated with the vent pipe wherein the valves arein operative association or communication with the control system,allowing the control system to open and close the valves respectively asneeded to send the steam or water to either a desired destination or tothe venting reservoir.